Prostate punctures, more particularly needle-biopsies, are carried out in a standard way through a transrectal ultrasonography. The ultrasonographic probe includes a puncture guide mechanically positioned so that the path of the puncture needle is in a/the sagittal acquisition plane of the probe. The positioning of the needle with respect to the organ is made through a visual guiding more particularly using the ultrasonographic pictures of said acquisition plane. For a 3D probe, “sagittal plane” will mean the probe “field of view” and, if need be, the mid-plane of the field of view.
In the case of the needle-biopsy, to carry out analyses, the practitioner will comply with a pre-defined puncture scheme of at least six punctures, with twelve being the standard. From this scheme, he/she must distribute the sampling in a homogenous way in the prostate area opposite the rectal probe head to optimise the chances of detecting a possible tumoral focus. The main difficulty consists in making a coherent distribution of the puncture points which can be optimum as regards the first diagnostic results on an organ which is not directly visible to an operator, which is not immobilized and which is deformed during the operation. The handling of the probe head thus requires both great skills and a strong experience to guarantee that the actual point of the sampling will match that on the scheduled puncture scheme.
This difficulty in guiding the puncture head to a theoretical target a fortiori implies the practitioner failing to know the exact position of the sampling carried out. This lack of information may lead to an incorrect diagnosis which is useless and also to repeated biopsies or to a non-focussed or at least a non-optimal therapy. The information on the intra-prostatic location of the puncture head is the key of a system for efficiently and globally treating prostatic pathologies and more particularly cancer.
International Application WO2005/110255
The international application WO2005/110255 provides for a solution for the targeting and the biopsy of tissues for medical purposes, and more particularly a targeted biopsy system, which enables the planning of the tissue to be sampled, the targeting of specific areas of the tissues, with reference to the plane, the capture of the tissue sample and the recording the source location of the tissue sample. The system is more particularly used for collecting samples of tissues from the prostate gland. It includes a flexible biopsy needle, a directional guide for said biopsy needle, imaging means, a biopsy scheme and recording means.
Drawbacks of Such Solution WO2005/110255
The problem entailed in this solution is that the identification of the prostate on the image is purely mechanical. Therefore, the image of the needle with respect to the prostate is calculated using a succession of references:
the “operation room” reference which makes it possible to determine the position of the probe using the support;
the “patient's body” reference which is likely to move with respect to the “operation room” reference;
the “organ” reference which is liable to move and be deformed with respect to the “patient's body” reference;
the “probe” reference which is theoretically stationary with respect to the “operation room” reference, but the mechanical connections are not absolutely rigid and thus lead to a possible shifting.
The image of the probe with respect to the prostate is thus calculated with an accumulation, or rather a multiplication of uncertainties and leads to localising the probe with respect to the prostate with several millimeters' inaccuracy. Therefore, the position of the sample with respect to the gland cannot be recorded nor used. Consequences are significant: the tumoral area is known only within several millimeters' accuracy, which entails treatments on needlessly large areas. Under these conditions, a therapeutic treatment, for example by local irradiation, cannot be focused on the tumoral area.
International Application WO2004/019799
From the international application WO2004/019799 is also known, in the prior art, a method to determine the position of a biopsy needle within a target volume, said target volume being defined as a space inside a patient. The method consists in:
generating several images of the target volume,
spatially recording the images for generating a three-dimensional representation of the target volume from the recorded images,
determining the location of the biopsy needle in the three-dimensional representation of the target volume, and
correlating the determined biopsy needle location with the spatially recorded images.
The graphic of the target volume includes a graphic representation of the determined location of the biopsy needle. This document also describes a locating technique wherein a camera tracking a reference target is fixed to an ultrasonographic probe, which enables an accurate localisation of the probe in a coordinate system. However, in the solution described in this document, the space inside the patient is not precisely defined: it can be interpreted as an assembly of tissues belonging to a patient or as a volume, the position and orientation of which are defined with respect to a coordinate system outside the patient.
In the first case, the system determines the position of the needle with respect to the patient's anatomy, whereas in the second case, the system determines the position of the needle with respect to a reference system outside the patient. In the second case, it is essential that the patient and the targeted organ do not move and are not deformed during the operation, or the position of the needle calculated in the targeted volume will not match the position of the needle with respect to the patient's anatomy.
It is clear, with the encapsulating volume and the reference system x-y-z as shown in FIG. 1 of such international application, as well as with the description of the locating methods (D1, p. 13 1.24-p. 14 1.35) that the system provided is in the second case. Several methods are provided, which all aim at localising the position of the ultrasonographic image with respect to an external and thus non-anatomic reference. The first method (D1, p. 13, 1.24-37) is stereotactic and localises the images with respect to the camera reference system. The second method is acoustic (D1, p. 13, 1.38-p. 14) and localises the images with respect to the pinger reference.
The third method provided (D1, p. 14, 1.5-1.35) is mechanical and thus consists in fixing the path of the needle using a guide with respect to the probe, and in immobilizing the prostate at the same time with a pawl to reduce the mobility thereof, and in determining the position of the probe (and thus of the needle) with a mechanical system (e.g. an encoded articulated arm), the identification for such system. The pawl makes it possible to reduce the movement of the prostate resulting from the movement of the probe but it cannot make up for the patient's motions (as he or she is locally anesthetised). As a summary, the system provided in the prior art document is capable of determining the needle with respect to an identification system inside the patient and thus requires that the targeted tissues do not move during the operation to obtain clinically satisfactory results.
Drawbacks of Such Solution WO2004/019799 and Solution Provided by the Invention
The claimed invention is based on a method for localising the needle with respect to an anatomic identification system, the latter being defined by a 3D reference image containing the targeted anatomy, i.e. the prostate. The matching of imaged tissues in the tracking images and reference images makes it possible to be independent of external localising systems such as those described in the international application WO2004/019799. The invention thus makes it possible to manage the “jumps” of patients which are well-known to the practitioners and which result from the pains caused upon the triggering of the biopsy gun, thanks to the utilisation of a purely anatomic identification system.
Patients jump approximately in 10 to 20% of transrectal prostate biopsies operations. The invention also makes it possible to avoid problems relative to the motions of the prostate more particularly resulting from the motions of the endorectal probe. The document WO2004/019799 does not provide the exploitation of one of the acquired images in order to determine the “reference image” relating to the initial position of the prostate.
The method provided in this document also aims at the same goal, but it implements a totally different means: it makes it possible to equip the external part of the probe with a camera which records the image of a pattern outside the patient and used for resetting the position of the probe. The part of the probe which remains outside the patient's body is provided with a camera which must be oriented to a stationary pattern for example glued on a wall of the operating block or the equipment supporting the patient.
The drawbacks of such solution are multiple:
it imparts constraints which are an obstacle to ergonomics and operation of the probe,
it provides an external reference in the operating block and not directly connected with the observation area, i.e. the prostate itself,
it does not make it possible to prevent the interferences resulting from the patient's untimely motions.
it implies the passage through a succession of references degrading the precision of the transformations:
“Operating block/patient's body” transformation,
“Operation room/prostate” transformation.
This document thus does not disclose the claimed characteristics and does not suggest these obviously for the persons skilled in the art.
International Application WO2006/089426
This document relates to a system and a method for performing a biopsy of a target volume and a computer device for planning the same. An ultrasonic transducer captures ultrasound volume data from the target volume. A three-dimensional recording module records the ultrasound volume data with supplementary volume data relative to the target volume. A biopsy planning module processes the ultrasound volume data and a supplementary volume data in combination in order to develop a biopsy plane for the target volume. A biopsy needle biopsies the target volume in accordance with the biopsy plane. A solution consisting in injecting a pre-operational “additional” image, on a per-operational “probing” image used for guiding a practitioner's gestures (§46 p. 13). The approach claimed in the present invention is different in that it aims at localising the organ during the punctures, with respect to a reference position.
The system described in the document WO2006/089426 also uses the localising of the images in a non-anatomic and external reference system to determine the position of the needle in the reference volume (FIG. 4, 108 and p. 22, 1.8-121 and §64 p. 16 with the support and MCM). The “three-dimensional” ultrasonography obtained with this method (FIG. 7, FIG. 8, FIG. 4 132, §139 p. 11) is different from the actual 3D ultrasonography on which an advantageous variant of the present claimed invention is based, as regards the quantity of available data, speed, collision and fineness of the 3D anatomic reconstruction. The system provided in the document WO2006/089426 is thus exposed to the same defects as those identified for the system disclosed in the document WO2004/019799. More particularly, the movements of the organ and, a fortiori, of the patient disturb the whole guiding method.